I cannot recommend where as I don't reside near the area in question. Whatever you do though, if you buy from a used dealer and particularly.... if you buy through a private sale, do certainly have a used vehicle history check performed. You can have this done for under a £fiver using the link below. This provides the past vehicle history that you need for your protection and offers an indemnity guarantee up to 5k in the unlikely event their information should later turn out to be incorrect.
https://www.mycarcheck.com/
Also; besides taking the car for a test drive to ensure you're happy, have an independent used vehicle inspection conducted by the AA or the RAC, this will provide an insight as to the mechanical condition and highlight any defects as well as providing information as to whether the car is worth the asking price.....before you agree to buy.